He sanded with too course of an abrasive, plain and simple. I seriously doubt that it is too course to polish out, but not being there, I can't say for sure. It probably needs to be sanded with 1000,1500,2000 then polish to get them out. If he polished through, all bets are off, it is repaint time.
My view on the engineer issue is he knows NOTHING about anything other than engineering. There is nothing wrong with that, engineering is HIS thing. You wouldn't believe how many times my brother the mechanic has heard "My husband could do it, he is a jet mechanic, he just doesn't have the time." Give me a break, Jet airplanes though more complex than a car are NOT the same thing. That is like a dentist "not wanting to take the time" to do a tonsillectomy.
The engineer should respect what I know about my trade as much as I respect him and his trade.
